198 SENSES HEARING. 



a strong pressure, the otolites crack in radiating lines, sepa- 

 rating often into four pyramidal pieces. This separation 

 also ensues, after a longer time, when the otolites are im- 

 mersed in a diluted nitric acid ; and if we touch them with 

 the concentrated acid, they suddenly dissolve with the disen- 

 gagement of a gas, whence Siebold concludes them to be 

 composed of carbonate of lime. The size of the otolites is 

 not equal ; and, in the same capsule there are always some 

 which are smaller than others. Within the capsule they 

 have, during life, a very remarkable and, in some respects, 

 peculiar, lively, oscillatory movement, being driven about as 

 particles of any light insoluble powder might be in boiling- 

 water. The otolites in the centre have the appearance of 

 being pressed together so as to form a sort of solid nucleus ; 

 and towards this centre the otolites towards the circumfe- 

 rence seem ever to be violently urged, their centripetal rush 

 being invariably repulsed, and as often driven again into a 

 centrifugal direction. Removed from the capsule, the mo- 

 tions of the otolites instantly cease. The cause of these 

 curious oscillations remains undiscovered. Siebold could 

 detect no vibratile cilia on the surfaces of the capsule ;* and 

 the cessation of the motion when the otolites are removed 

 proves them to be unciliated themselves, and, at the same 

 time, distinguishes the motion from that of inorganic mole- 

 cules as described by Mr. Brown. -j- 



And in these discoveries you have a lively example of the 

 nicety of anatomical researches in our times. In my student 

 clays, it was questioned whether any mollusk besides the 

 cuttles had eyes ; J and it was agreed on all hands that they 

 were earless and surd.§ Behold the change a few years has 

 made in our knowledge of this branch of physiology ! They 

 have eyes and they see ; and ears have they, yet, from the 

 very rudimentary condition of the organ, it is adapted to 

 communicate to the possessors only the most limited per- 

 ception of sonorous undulations. Amusing myself with 



* " Kolliker has observed, that the motion of the otolites in the mollusca 

 is dependent upon cilia, with which the internal surface of the cyst is cover- 

 ed." — Reports on Zoology for 1843-4, printed for the Ray Society, p. 216. 



t Observations sur l'Organe Auditif des Mollusques, par C. Th. V. Sie- 

 bold, in Ann. des Sc. Nat. (1843), xix. p. 193—211. 



| "Vermium genus omne oculis caret; Plin. nisi forte Sepia ejusque 

 Cymbium. Limaces videntur ctiam oculis instructi, modo verr sint oculi, a 

 nostris certe diversi." — Linn. Syst. Nat. 1069. 



§ " None of the mollusca appear to possess, even in the smallest degree, 

 the sense of hearing, if we except the highly organized Cephalopoda." — 

 Roget's Bridgeiv. Treat, ii. 436. 



